Control device



' Aug. 7, 1945. c. K. STROBEL CONTROL DEVICE Filed June 22, 1942INVENTOR. (harks jgdtrobeb.

[WW/m ATTORNEK Patented Aug; 7, 1945 ,784

omfrso STATES PATENT OFFICE 2,381,784 GONTR-OL DEVICE Charles K.Strobe], Pittsburgh, Pa., assign'or to Robertshaw Thermostat Company,Youngwood, Pa., a corporation of Pennsylvania Application June 22, 1942,Serial No. 447,933 4 Claims. "('01. 200-122) l'liisinvention relates tocontrol devices and, Positioned adjacent the support l2 andproparticularly, to electrc-thermally operated jecting from the basemember In is a post 34 upon relays. which the electro-thermal means ismounted. In

An object of the invention is to incorporate a this embodiment, thismeans comprises a bitii'ne-delay period of substantial uniformity fol 5metal strip 36 secured at one end to the post 34 lowing initialoperation and prior to actual opand having depending from its oppositeend an eration of the control. electromagnet 3B the core 40 of which hassufll- Another object of the invention is to render cient verticaldimension to overlap the adjacent the time-delay period substantiallyconstant irside of the armature bar IS in both directions. respective ofvariables in the electro-thermal 10, The bimetal strip is an elementadapted to deconrlitions. liect upwardly or away from base l when[Another object of the invention is to permit heated. In addition to thesupport provided for rapid on cii on operation or recycling followingthe armature bar l6 by the support I2, the opprolcneed operation of thecontrol while retain- P0 6 end t e efi rest-S p a Shoulder 44 the timedelay interval unimpaired. formed on a pin 42 carried by-the base Illand Another object of the invention is to maintain which projectsthrough an aperture formed in sulcstantiaiuniformity of delay periodthroughthe armature bar I6 for the purpose. The annaout many recyclingoperations in rapid succesture bar may be urged into en ag ment wi h hea: shoulder 44 by means of a spring 46 extending Other objects andadvantages will become apbetween. the base I 0 and the armature l6interparent from the following description taken in mediate the pin 42and the support l2. connection with the accompanying i The electricalconnections for the structure so "wherein far described may includemeans for heating the Fig. l is an elevation in schematic form of aelement comprising a heating Coil 43 50 P08 eontroi device constructedin accordance with ned re t e to e St p 36 that a majo D the invention;tion thereof receives heat when the coil 48 is Fig 1 1 aplan view of tsame; energized. One end of the coil 48 is connected Fig. 2 is anelevation in schematic form showby a i e i to a wi 51 leading r oneering a modified arrangement of t in parts of minal of the secondary Ofa transformer 54, while the control devi e; n the opposite end of thecoil 48 is connected by a Fig. 2A is a plan vi f th same wire 56 to oneterminal of the electromagnet 38.

Referring more particularly to the drawing The circuit in which the C01143 s connected y and specificall to Fi s, 1 and 1 t control further betraced by way of wire 58 from the device of this arrangement maycomprise a base other terminal f electromagnet 38 to one end member Hihaving a support I: t one thereof a resilient conductor 60, by wire 62to'the conhg' ppm idea t a rectangular or other mm tact I8, from contact22 by wire 64 to resilient al.3111211, projectmn H to receive thesuitably conductor 68 and by wire 88 to wire 10 connected slotted end ofa movable armature device, such to one terminal of a main switch H theother an armature bar 6' The armature bar Is is terminal of which isconnected to the other terpreierably made 01' iron and carries twospaced mmal of the transformer secondaryinsulated contacts l8 and 20 atthe end remote fi f ffll i gnz i i c il n i the1 glgfitrlcz from thesupport l2 and which cooperate re 9 a s I spectiveiy with similarcontacts 22 and 24 each fi ig g g z 2; 3 2 25 23232;

arre f g g g g iz ss g i ig z fg i fi g g by a wire 16 to any otherelement or Series of 3 an elements included in the circuit. Such elementiorm with contacts 20 and 24 two contact mug p or elements designated bythe numeral 18 are P11 which cqmacts and u the shown connected in serieswith the element 12 to t ,opposlte. end of each leaf f 25 be controlled,such circuit being completed by the is damped In a post 28 mounted onthe adlacent wire 80 connected to the wire 10. A shunt is esf Q f basemember and surmounted by a tablished around the element 12 to becontrolled pair or arms 36 each carrying an adjustment by means of a w82 indicated in Fig, 1A as exscrew or other device by means of whichtending from one end of the element '12 to the movement Of the leaf sprigs 26 in response to contact 20 and by a wire 84 likewise indicated niasthereof may be limited. as extending om e Opposite end of the ment 1! tothe contact 24. Thus, elements 18 and 12 are in series circuit; coil 48,electromagnet 08, and contacts, I8-22 are in another series circuit andare also in parallel circuit with elements I8 and II.

In the operation of the device so far described, the main switch II isclosed, causing energization of the heating coil 48, electromagnet 38and the elements of the main circuit designated by the numeral 10. Asthe contacts I8, 22, 20 and 04 are at this time closed, the shuntestablished for element I2 to be controlled is effective and thiselement receives insufficient current to become operative. Theelectromagnet 30 being energized, the core 40 thereof engages thearmature bar I8 in its lowest position and simultaneously the heatingcoil 48 begins to heat and cause the bimetal strip 08 to deflectupwardly. Due to the attraction of the armature bar ll by theelectromagnet core 40, a joint upward movement occurs but the contactsremain closed until the leaf spring 28 associated with each contact 22and 24 engages the end of the adjusting screw 32 therefor and is thusprevented from moving any further under its bias. Opening of thecontacts 'thus occurs after a predetermined time-delay period which isset by the time required for the heating coil 48 to heat and cause thebimetal strip 88 to deflect sufficiently to open the contacta. In thearrangement shown, opening or the contacts removes the shunt from theelement. I! which thereupon becomes operative alter me specifiedtime-delay period. However, in the arrangement thus far described (whichdescription is as yetincomplete as to the features of this invention)the opening of the contacts would cause deenergizationof the heater coil48 and electromagnet 38 with consequent return of the armature bar I8 toits initial position. Such operation would cause reclosing of thecontacts "-42. and the second pair of contacts 20-44 unless means wereprovided to prevent this occurrence.

To this end, a holding circuit for the armature bar I is provided andmay comprise a second electromagnet 86 having one terminal thereofconnected by a wire 08 to the wire 82 and the other terminal thereofconnected by a wire 00 to the wire I0. Consequently, electromagnet 88 isenergized when switch II is closed. This holdin circuit is thus separatefrom the two previously described and places electromagnet 08 inparallel circuit with the heater coil 40 and other elements of thecircuit in which the coil is connected; The electromagnet 86 issupported from the base ID in spaced relation to the armature bar I8 inits initial position but arranged so that the core 02 thereof ispositioned to engage the armature bar l8 in its tilted positionimmediately prior to opening of the contacts I8--22. The electromagnet88 is of suflicient strength to engage and hold the armature bar I8 onlyafter the armature has been lifted partially by the elec tromagnet 38.Thus, when the contacts are opened by the leaf springs 28 engagingscrews 32, the armature bar I8 is held in tilted position by the holdingmagnet 88 which remains energized due to its connection in a separatecircuit. The

holding circuit preferably becomes efiective im-.

mediately prior to the time when the contacts open but it will beapparent that a simultaneous action may be provided.

The heater coil 48 then begins to cool. If cooling proceeds to ambienttemperature, the bimetal strip 36 and attached magnet 38 will return totheir original positions. However, even if the bimetal strip does notcool completely before switch II is opened and then immediatelyreclosed, a time-delay substantially equal to the original period willbe obtained.

Hence, should such recycling operation be conducted several times insuccession, the overlapping arrangement of the core 40 with respect tothe side of armature bar I8 will ensure the bar being within the fieldof the electromagnet 30, although the bimetal strip 38 does not havetime to cool completely. It will furthermore be apparent that if thedevice I2 to be controlled is maintained in operation for a lengthyperiod, the temperature of the bimetal 86 is not continuously increasedduring such period to its saturation point where the strip can deflectno further but, on the contrary, the period is utilized to provide timefor the strip to cool sufficiently to regain its original position.

The relay thus described is intended to operate on alternating currentfrom the secondary of the transformer 54. It will be understood that inthis event the iron parts of the electromagnets and armature will beappropriately made. If it is desired to operate from such a currentsource while utilizing direct current magnets then suitable rectiflerscould be incorporated in the device.

As an example of the use to which the control device of this inventionmay be put, the circuit element I8 may comprise an ignition coil adaptedto ignite a fuel burner when energized. The element 12 to be controlledmay comprise a normally closed electromagnetic valve interposed in thefuel line and adapted to be opened only after the ignition coil hasreached igniting temperature. Thus. upon closing of the main switch I Ithe electrornagnetic fuel valve would remain closed due to the shunteffective as long as the second pair of contacts 20 and 24 remain closedand this valve would not be opened to admit fuel to the burner untilafter the time-delay interval set by the bimetal 38 had caused openingof the contacts. During this interval the igniter coil would havereached igniting temperature and, as soon as the contacts open to removethe shunt and open the fuel valve, the fuel would be ignited by theignition coil. This and other examples of systems having means to beoperated at a predetermined interval following energization of thecircuit wherein it is connected will occur to those skilled in the art.

In Figs. 2 and 2A a modified form of coupling arrangement between thebimetal strip and the contacts has been provided. Where parts similar tothose disclosed in Figs. 1 and 1A are used similar reference numeralshave been applied. Thus, the base member I0 supports a post I00 providedwith an horizontal pivot I02 for a contact carrying bar I04 which is notnecessarily iron or other magnetically attractive material. The oppositeend of the bar I04 carries the spaced contacts i8 and 20 arranged as inthe preceding embodiment. A pin I08 positioned adjacent the contacts andabutting the underside of the bar I04 serves to support the bar I04 andis carried by the base member I0. As in the preceding embodiment, aspring 46 biases the armature I04 downwardly against the pin I08.

In this embodiment, the bimetal strip I08 carries the electromagnet IIOdepending therefrom and having a core H2 overlapping in vertical dithisinstance, however, slot I14 extending ionmension the bar I04. In the baris provided with a heating by the heating coil 48.

the core] I2 and serve to maintain the armature I20 in alignment withthe core I I2. armature I24 is mounted on the bar An auxiliary I04 inoperative relation with the electromagnet 06 and adapted to be attractedthereby after the bar has *moved it into an appropriate part of themagnetic field of the electromagnet. The heater adapted to attract saidarmature device after said movement has continued for. apredeterminedperiod and to retain it in said one position with saidcontacts disengaged, said element thereby becoming unheated andreturning toward 'undeflected position, and a second pair of contactsadapted for joint operation with the first said contact pair when gs'aidarmature device reaches said position to/control a circuit extendingthrough said second contact pair.

" 3. An electro-thermal relay comprising a movcoil 48 for the bimetalI08, together with theremaining parts of the device, may be preciselythe same as those described in connection with the previous embodimentand further I 'descriptionis deemed unnecessary. The modifiedarrangement permits free upward motion or the bar I04 when theelectromagnet H0 is energized'so that the core H2 thereof engages thearmature I20 and the bimetal strip I08 deflects upwardly due to As soonas the auxiliary armature I24 has moved a predetermined distance intojuxtaposition to core 92 the bar I04 is held after the bimetal deflectsdownwardly due'to opening of the contacts I8 and 22.

While the invention has been described and shown in its preferredembodiments, it will be understood that many changes may be made in thearrangement of parts and details of construction without departing fromthe spirit of the invention as expressed in the appended claims.

I claim:

1. An electro-thermal relay comprising a movable armature device, a pairof initially closed contacts adapted to be opened upon movement of saidarmature device to one position, said contacts remaining closed untilsaid armature device reaches said position, an element adapted todefiect when heated and cause movement of said armature device towardsaid position, means effective when said contacts are closed for heatingsaid element and being ineffective for said purpose when said contactsare opened, an electromagnet adapted to attract said armature deviceafter said movement has continued for a predetermined period and toretain it in said one position with said contacts opened, said elementthereby becoming unheated and returning toward undefiected position, anda second pair of contacts adapted for joint operation with the firstsaid contact pair when said armature device reaches said position tocontrol a circuit extending therethrough.

2. An electro-thermal relay comprising a movable armature devicecarrying a contact, a springmountedcontact initially engaging saidarmature contact, means for disengaging said pair of contacts tointerrupt a circuit extending therethrough upon movement of saidarmature device to one position, said contacts remaining engaged untilsaid armature device reaches said position, an element adapted todeflect when heated and cause movement of said armature device towardsaid position, a heater coil connected in said circuit for heating saidelement in response to current flow through said coil when said contactsare engaged, an electromagnet able armature device carrying a contact,-a springmounted contact initially engaging said armature cbntact, meansfor disengaging said pair of contacts to interrupt a circuit extendingtherethrougl lupon movement of said armature device to one ,position,said contacts remaining engaged until said armature device reaches saidposition,

an electromagnet connected in said circuit and ad pted to attract saidarmature device during the period that said contacts are engaged and torelease said armature device upon said contact disengagement, an elementsecured to said electromagnet and adapted to deflect when heated forcausing movement of said armature device toward said position, a heatercoil connected in said circuit for heating said element in response tocurrent flow through said coil when said contacts are engaged, a secondelectromagnet adapt. ed to attract said armature device after saidmovement has continued for a predetermined period and to retain it insaid one position with said contacts disengaged, said element therebybecoming unheated and returning toward undefiected position, and asecond pair of contacts adapted for joint operation with the first saidcontact pair when said armature device reaches said position to controla circuit extending through said second contact pair.

4. An electro-thermal relay comprising an armature device pivoted at oneend for relative movement at the other, two contacts carried on saidother end of the armature device, two springmounted contacts eachadapted to engage with a related one of said armature contacts to formtwo contact pairs, means for restraining said spring-mounted contactsfrom following movement of said armature contacts and causingdisengagement therebetween after a limited joint movement of said pairs,a circuit controlled by one of said contact pairs, an electromagnetconnected in said circuit and adapted to attract said armature deviceat'the inception of said joint contact movement, a bimetal stripcarrying said electromagnet and operable when heated for causing saidarmature device movement, a heater coil connected inseries circuit withsaid electromagnet for heating said strip in response to current flowthrough said coil when said one contact pair is engaged, a secondelectromagnet connected in another circuit and adapted to attract saidarmature device substantially simultaneously with operation of saidrestraining means to disengage said contact pairs, said strip therebybecoming unheated while said armature device remains in attractedrelation with said second electromagnet for maintaining both contactpairs disengaged, and a third circuit controlled by the other of saidcontact pairs.

CHARLES K. S'I'ROBEL.

